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Hypersonic vehicles have strong maneuverability, and the method of trajectory prediction is different from traditional aircrafts. The current research on hypersonic vehicle trajectory prediction is usually aimed at the full trajectory prediction, and there are few methods for hypersonic vehicle trajectory prediction in specific scenes. In this paper, aiming at the scene that hypersonic vehicle be not observed in the blind area of land-based radar, a trajectory prediction method of hypersonic vehicle is proposed, which is realized by predicting the control quantity. According to the constraint characteristics, aerodynamic characteristics and motion characteristics, the characteristic function is established. And on the basis of the priori information from the observed data, the conditional random field model is established to predict the control quantity. The trajectory in the blind area is calculated according to the predicted control quantity. Finally, the effectiveness and feasibility of the trajectory prediction method proposed in this paper are verified by case study.

With an increase of service users’ demands on high quality of services (QoS), more and more efficient service computing models are proposed. The development of cloud computing, fog computing, and edge computing brings a number of challenges, e.g., QoS optimization and energy saving. We do a comprehensive survey on QoS optimization and energy saving in cloud computing, fog computing, edge computing, and IoT environments. We summarize the main challenges and analyze corresponding solutions proposed by existing works. This survey aims to help readers have a deeper understanding on the concepts of different computing models and study the techniques of QoS optimization and energy saving in these models.

In order to improve the attitude measurement accuracy of the stratospheric airship, a stochastic process of damped oscillation autocorrelation is proposed to model the attitude angular velocity of the stratospheric airship, and the state transition matrix and the process noise covariance matrix of the model are derived. Based on this, the Kalman filter algorithm is used to correct the attitude angle measurement of the stratospheric airship. Finally, the model is compared with Singer model, Jerk model and sinusoidal correlation model by simulation experiment and the influence of parameter selection on model effect is analyzed. The results demonstrate the effectiveness and advantages of the proposed model in correcting the attitude angle of the stratospheric airship.

Based on the gas-liquid phase equilibrium and multi-component diffusion theory, an analytical model for predicting acid dew point temperature and vapour condensation characteristics of flue gas was developed. The effects of components content, ash particle radius, wall temperature, coal-burned type and excess air ratio have been investigated. The results indicated that the acid dew point temperature and vapour condensation rate will increase with both water and sulfuric acid vapour contents increase. Vapours are not prone to condense on the ash particles when the particle radius is less than the corresponding critical condensing radius. The vapour condensation characteristics can be divided into two different stages with the wall temperature varies. The particle radius has a significant influence on the vapour condensation characteristics in the higher temperature stage. The acid dew point temperatures present significant differences for different coal-burned types, and the water vapour condensation rate is more sensitive to excess air ratio compared with the acid condensation rate.

Aiming at the interference problem of wind turbine blade to air tube radar, this paper proposes a wind turbine blade echo model based on LFM signal. The model considers the variation characteristics of wind turbine echo signals with blade rotation, establishes the relevant echo amplitude model and phase model, and discusses the electromagnetic scattering characteristics of wind turbine blades under different conditions. The characteristics of wind turbine blade echo signals in time domain, frequency domain and time-frequency domain are studied by using the proposed model. The influence of wind turbine blades on radar signal processing is analysed. Simulations demonstrate the effectiveness of the signal model.

Two difficulties are always encountered in the simulation of variable density low Mach number flows by the primitive variable methods: (1) the decoupling of pressure and velocity caused by the extremely small velocity; (2) the spurious oscillations, nonsmooth solutions and sharp resolution caused by discontinuities, making that the flow cannot be successfully simulated by low-ordered schemes. In this paper, a pressure-based compressible flow solver with a scheme of high-resolution is developed to overcome these difficulties. In the present work, we adopt pressure correction algorithm to overcome the decoupling and the MUSCL scheme to predict the discontinuities at low Mach number. We applied the proposed compressible flow solver to simulate the compressible flows in a planar nozzle, arc bumps and the lid-driven cavity and found that the numerical results are in good agreement with those reported in the previous works, indicating that the numerical algorithm developed in this work is a reliable and accurate tool for studying thermal variable density low Mach number flows.

recently, with the more extensive deployment of Wireless Local Area Networks (WLAN), and the growing population of mobile users, the unstable handover problem in wireless network services receives more and more attention. Since users expect the continuity of services while roaming, IEEE 802 family defines the standard IEEE 802.11r (Fast BSS Transition) to reduce the interrupted time of services to the minimum. Supposing users use IEEE 802.11r to execute the pre-authentication process with all Access Points, there will be too many authenticated messages. Therefore, an IEEE 802.11rbased algorithm is proposed to avoid the pre-authentication process with all APs. In order to reduce the pre-register APs, we first of all divide the coverage of the APs into four regions according to the RSSI. Second, to figure out more accurate APs, we dynamically adjust the region. Third, if the mobile device cannot find the AP of each region, we further modify the region. Finally, we pick up an AP to execute the preauthentication each region. With the four above-mentioned considerations proposed in this algorithm, we are able to make use of roaming more effectively.

Aiming at solving the problem of detection performance degradation of CA-CFAR and OS-CFAR in the circumstance of multi-targets and strong interference, a CFAR whose selection of reference samples is based on statistics of the CUT (Cell-Under-Test) is presented. Simulation shows that this CFAR suffers a small CFAR loss compared to CA-CFAR in homogeneous environment, and performs robustly against interferers in a non-homogeneous environment.